bisecting fixing commit since abf02e2964b3aaf1d5197c5d7c671e771b0e109e building syzkaller on 34bf9440bd06034f86b5d9ac8afbf078129cbdae testing commit abf02e2964b3aaf1d5197c5d7c671e771b0e109e with gcc (GCC) 8.1.0 kernel signature: 766c1ebdffdec83ec6449b4bcec579b8f0e2e51113bedc3a7e4f5c6591d378d0 run #0: crashed: INFO: rcu detected stall in sys_sendfile64 run #1: crashed: INFO: rcu detected stall in sys_sendfile64 run #2: crashed: INFO: rcu detected stall in sys_sendfile64 run #3: crashed: INFO: rcu detected stall in ext4_file_write_iter run #4: crashed: INFO: rcu detected stall in ext4_file_write_iter run #5: crashed: INFO: rcu detected stall in sys_sendfile64 run #6: crashed: INFO: rcu detected stall in sys_sendfile64 run #7: crashed: INFO: rcu detected stall in ext4_file_write_iter run #8: crashed: INFO: rcu detected stall in ext4_file_write_iter run #9: crashed: INFO: rcu detected stall in ext4_file_write_iter testing current HEAD b85051e755b0e9d6dd8f17ef1da083851b83287d testing commit b85051e755b0e9d6dd8f17ef1da083851b83287d with gcc (GCC) 8.1.0 kernel signature: ac80610912eea35606f84fc1aa3c3637be9e95c5061884e97f77e0f5adcbea8b run #0: crashed: INFO: rcu detected stall in ext4_file_write_iter run #1: crashed: INFO: rcu detected stall in ext4_file_write_iter run #2: crashed: INFO: rcu detected stall in sys_sendfile64 run #3: crashed: INFO: rcu detected stall in sys_sendfile64 run #4: crashed: INFO: rcu detected stall in sys_sendfile64 run #5: crashed: INFO: rcu detected stall in ext4_file_write_iter run #6: crashed: INFO: rcu detected stall in corrupted run #7: crashed: INFO: rcu detected stall in ext4_file_write_iter run #8: crashed: INFO: rcu detected stall in sys_sendfile64 run #9: crashed: INFO: rcu detected stall in ext4_file_write_iter revisions tested: 2, total time: 22m15.844621528s (build: 11m33.346362427s, test: 9m46.392767013s) the crash still happens on HEAD commit msg: Merge tag 'fixes-for-5.7-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux crash: INFO: rcu detected stall in ext4_file_write_iter rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: (detected by 0, t=10502 jiffies, g=6357, q=328) rcu: All QSes seen, last rcu_preempt kthread activity 10503 (4294953159-4294942656), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor.4 R running task 26928 7569 6688 0x00004000 Call Trace: sched_show_task.cold.101+0x2ee/0x35d kernel/sched/core.c:5956 print_other_cpu_stall kernel/rcu/tree_stall.h:430 [inline] check_cpu_stall kernel/rcu/tree_stall.h:558 [inline] rcu_pending kernel/rcu/tree.c:3225 [inline] rcu_sched_clock_irq.cold.87+0xaa3/0xc50 kernel/rcu/tree.c:2296 update_process_times+0x23/0x50 kernel/time/timer.c:1727 tick_sched_handle+0x77/0x140 kernel/time/tick-sched.c:176 tick_sched_timer+0x43/0x100 kernel/time/tick-sched.c:1320 __run_hrtimer kernel/time/hrtimer.c:1520 [inline] __hrtimer_run_queues+0x524/0xc00 kernel/time/hrtimer.c:1584 hrtimer_interrupt+0x2df/0x760 kernel/time/hrtimer.c:1646 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1113 [inline] smp_apic_timer_interrupt+0x163/0x5f0 arch/x86/kernel/apic/apic.c:1138 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:759 [inline] RIP: 0010:seqcount_lockdep_reader_access include/linux/seqlock.h:83 [inline] RIP: 0010:read_seqcount_begin include/linux/seqlock.h:164 [inline] RIP: 0010:ktime_get_coarse_real_ts64+0x192/0x210 kernel/time/timekeeping.c:2165 Code: c3 e8 b2 7f 12 00 48 c7 c7 a0 6c 94 88 48 89 f8 48 c1 e8 03 42 80 3c 38 00 75 5b 48 83 3d f5 72 37 07 00 74 23 48 89 df 57 9d <0f> 1f 44 00 00 e9 54 ff ff ff f3 90 8b 02 a8 01 0f 84 5d ff ff ff RSP: 0018:ffff8880864374b0 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13 RAX: 1ffffffff1128d94 RBX: 0000000000000282 RCX: 0000000000000006 RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000282 RBP: ffff8880864374e8 R08: 0000000000000006 R09: fffffbfff141ca35 R10: ffffffff8a0e51a7 R11: fffffbfff141ca34 R12: ffff888086437518 R13: fffffbfff1128d95 R14: ffffffff88946c98 R15: dffffc0000000000 current_time+0x66/0xf0 fs/inode.c:2205 file_update_time+0xef/0x380 fs/inode.c:1893 file_modified+0x53/0x70 fs/inode.c:1933 ext4_write_checks+0x37/0x60 fs/ext4/file.c:249 ext4_buffered_write_iter+0xa7/0x3d0 fs/ext4/file.c:265 ext4_file_write_iter+0x1b7/0x13b0 fs/ext4/file.c:642 call_write_iter include/linux/fs.h:1907 [inline] do_iter_readv_writev+0x532/0xa70 fs/read_write.c:694 do_iter_write+0x130/0x510 fs/read_write.c:999 vfs_iter_write+0x5b/0xb0 fs/read_write.c:1040 iter_file_splice_write+0x576/0xb70 fs/splice.c:760 do_splice_from fs/splice.c:863 [inline] direct_splice_actor+0x104/0x1c0 fs/splice.c:1037 splice_direct_to_actor+0x345/0x960 fs/splice.c:992 do_splice_direct+0x158/0x280 fs/splice.c:1080 do_sendfile+0x4a9/0xe30 fs/read_write.c:1521 __do_sys_sendfile64 fs/read_write.c:1576 [inline] __se_sys_sendfile64 fs/read_write.c:1568 [inline] __x64_sys_sendfile64+0x12e/0x1e0 fs/read_write.c:1568 do_syscall_64+0xca/0x630 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x4592c9 Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fa105dd3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00000000004592c9 RDX: 0000000020000000 RSI: 0000000000000003 RDI: 0000000000000003 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 00008080fffffffe R11: 0000000000000246 R12: 00007fa105dd46d4 R13: 00000000004c689d R14: 00000000004db828 R15: 00000000ffffffff rcu: rcu_preempt kthread starved for 10554 jiffies! g6357 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 rcu: RCU grace-period kthread stack dump: rcu_preempt R running task 29096 10 2 0x80004000 Call Trace: context_switch kernel/sched/core.c:3367 [inline] __schedule+0x85b/0x1950 kernel/sched/core.c:4083 schedule+0xc3/0x2b0 kernel/sched/core.c:4158 schedule_timeout+0x2bd/0x710 kernel/time/timer.c:1898 rcu_gp_fqs_loop kernel/rcu/tree.c:1674 [inline] rcu_gp_kthread+0x9da/0x1a40 kernel/rcu/tree.c:1836 kthread+0x354/0x420 kernel/kthread.c:268 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:351